(meteorobs) Meteor Activity Outlook for August 15-21, 2009

[Robert Lunsford]

Meteor activity kicks into high gear in August as seen from the northern
hemisphere. The main reason for all this activity is the Perseid shower that
peaks on August 12. This shower is active most of the month and remains
above the level of the sporadic background for a week centered on August 12.
The sporadic activity is also increasing as seen from the northern
hemisphere and is now nearly double the rates from just three months ago. As
seen from south of the equator, meteor rates are still decent but falling
rapidly. The sporadic rates seen at the beginning of the month will be twice
as much as those seen during the last days of the month. The Perseid radiant
does not rise high into the sky as seen in the southern hemisphere so rates
from this shower are greatly reduced when compared to the northern
hemisphere.

During this period the moon reaches its new phase on Thursday August 20th.
At that time it will rise and set with the sun and will not be visible at
night. This weekend the waning crescent moon will not pose much of a problem
as long as meteor observers keep it out of their field of view. The
estimated total hourly rates for evening observers this week is near six as
seen from the northern hemisphere and three from the southern hemisphere.
For morning observers the estimated total hourly rates should be near twenty
two from the northern hemisphere and sixteen as seen from the southern
hemisphere. The actual rates will also depend on factors such as personal
light and motion perception, local weather conditions, alertness and
experience in watching meteor activity.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning August 15/16. These positions do not change greatly day
to day so the listed coordinates may be used during this entire period. Most
star atlases (available at science stores and planetariums) will provide
maps with grid lines of the celestial coordinates so that you may find out
exactly where these positions are located in the sky. A planisphere or
computer planetarium program is also useful in showing the sky at any time
of night on any date of the year. Activity from each radiant is best seen
when it is positioned highest in the sky, either due north or south along
the meridian, depending on your latitude. It must be remembered that meteor
activity is rarely seen at the radiant position. Rather they shoot outwards
from the radiant so it is best to center your field of view so that the
radiant lies at the edge and not the center. Viewing there will allow you to
easily trace the path of each meteor back to the radiant (if it is a shower
member) or in another direction if it is a sporadic. Meteor activity is not
seen from radiants that are located below the horizon. The positions below
are listed in a west to east manner in order of right ascension (celestial
longitude). The positions listed first are located further west therefore
are accessible earlier in the night while those listed further down the list
rise later in the night.

The following showers are expected to be active this week:

The Kappa Cygnids (KCG) are active from a wide radiant located at 19:00
(285) +59. This position is located in southern Draco, five degrees
northwest of the fourth magnitude star Kappa Cygni. Current rates would be
near one shower member per hour. With an entry velocity of 25 km/sec. most
of these meteors will appear to travel slower than average. The radiant is
best placed near 2300 Local Daylight Time (11pm LDT) when it lies nearly
overhead for much of the Northern Hemisphere. Due to its high northern
declination this activity is not well seen from the Southern Hemisphere.

The large Antihelion (ANT) radiant is now centered at 22:24 (336) -08. This
area of the sky lies in central Aquarius, just east of the fourth magnitude
star Theta Aquarii. Actually any meteor from Aquarius, eastern Capricornus,
as well as western Pisces, could be a candidate for this shower. This
radiant is best placed near 0200 LDT when it lies on the meridian and is
highest in the sky. Rates at this time should be near three no matter your
location. With an entry velocity of 30 km/sec., the average Antihelion
meteor would be of medium-slow speed.

The Delta Aquariids (SDA) are active from a radiant at 23:28 (352) -12. This
position lies in eastern Aquarius, four degrees southeast of the fourth
magnitude star Psi 2 Aquarii. The radiant is best placed near 0300 LDT, when
it lies highest in the sky. Current hourly rates would be one from the
northern hemisphere and two as seen from south of the equator. With an entry
velocity of 43 km/sec., most activity from this radiant would be of average
velocities.

The Perseids (PER) peaked on August 12th with good rates despite the
unfavorable lunar conditions. The current radiant position lies at 03:28
(052) +58, which is located in southern Camelopardalis, eight degrees north
of the second magnitude star Mirfak (Alpha Persei). The radiant is well
placed for those in the northern hemisphere during the last few hours before
dawn. Due to the high northern declination (celestial latitude) of the
radiant, rates witnessed from the southern hemisphere are very low when
compared to those seen north of the equator. Current hourly rates would be
five from the northern hemisphere and two as seen from south of the equator.
At 59 km/sec., Perseid meteors are swift, often exhibiting persistent
trains.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are
becoming more active. One would expect to see approximately thirteen random
meteors during the last hour before dawn from rural observing sites and
three per hour during the evening hours. As seen from the mid-southern
hemisphere (45S) morning rates would be near nine per hour as seen from
rural observing sites and two per hour during the evening hours. Locations
between these two extremes would see activity between the listed figures.

The table below presents a summary of the expected activity this week. Rates
and positions are exact for Saturday night/Sunday morning August 15/16, but
may be used all week.

Kappa Cygnids (KCG) 19:00 (285) +59 Velocity - 25km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - <1 per hr.

Antihelion (ANT) - 22:24 (336) -08 Velocity - 30km/sec.
Northern Hemisphere - 3 per hr. Southern Hemisphere - 3 per hr.

Delta Aquariids (SDA) 23:28 (352) -12 Velocity - 43km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - 2 per hr.

Perseid (PER) 03:28 (052) +58 Velocity - 59km/sec.
Northern Hemisphere - 5 per hr. Southern Hemisphere - 2 per hr.

 *For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2009

Clear Skies!
Robert Lunsford
American Meteor Society